bweuler (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Compute the Euler number of a binary image

Syntax

```
eul = bweuler(BW,n)
```

Description

eul = bweuler(BW,n) returns the Euler number for the binary image BW. The return value eul is a scalar whose value is the total number of objects in the image minus the total number of holes in those objects. The argument n can have a value of either 4 or 8, where 4 specifies 4-connected objects and 8 specifies 8-connected objects; if the argument is omitted, it defaults to 8.

Class Support

BW can be numeric or logical and it must be real, nonsparse, and two-dimensional. The return value eul is of class double.

Example

BW = imread('circles.png');
imshow(BW);


bweuler(BW)

ans =

    -3

Algorithm

bweuler computes the Euler number by considering patterns of convexity and concavity in local 2-by-2 neighborhoods. See [2] for a discussion of the algorithm used.

See Also

bwmorph, bwperim

References

[1] Horn, Berthold P. K., Robot Vision, New York, McGraw-Hill, 1986, pp. 73-77.

[2] Pratt, William K., Digital Image Processing, New York, John Wiley & Sons, Inc., 1991, p. 633.

bwdist bwhitmiss